Idiots dropping ecstasy annoyed judge (8)
I believe the answer is:
assessor
'judge' is the definition.
(I've seen this before)
'idiots dropping ecstasy annoyed' is the wordplay.
'idiots' becomes 'asses' (I've seen this before).
'dropping' is a deletion indicator (some letters drop out).
'ecstasy' becomes 'E' (informal term for the drug).
'annoyed' becomes 'sore' (I've seen this in another clue).
'sore' with 'e' removed is 'sor'.
'asses'+'sor'='ASSESSOR'
(Other definitions for assessor that I've seen before include "property valuer" , "In his estimation" , "Maker of valuations" , "One estimating value" , "Person who tests" .)